This invention relates to tissue laminates and to methods of combining tissue layers with continuous filament nonwoven layers to produce strong, pliable and quiet cloth-like tissue laminates. The present laminate exhibits a characteristics and unexpected low level of the paper-like rattle heretofore present in such tissue laminates and can be produced as liquid absorbent and/or repellent cloth-like laminates as sheet materials suitable for use as surgical draping, clothing, toweling, bed clothing, tenting and other uses normally reserved to woven materials.
Specifically, the invention consists of impregnating a low basis weight, lightly bonded or unbonded, continuous filament central layer with soft, tacky, pliable nonmigratory latex solids applied from viscous emulsions. The impregnated central layer of continuous filament nonwoven material is thereafter combined between at least two, facing layers of absorbent, soft tissue paper while in the moist state. The combining is accomplished with low pressures prior to drying and curing the resulting laminate sheet material. The product laminate can be made fire resistant, highly liquid absorbent and/or repellent. Conventional post treatments such as button breaking, micro-creping, surface brushing and conventional dry or wet creping can also be accorded to the dried and cured laminate to further enhance its softness, handle and drape.
Heretofore, tissue laminates having been prepared by a variety of methods using various central and facing layers and achieving greater or lesser success in achieving cloth-like laminate properties. In certain instances, the resulting laminates have been provided with scrim materials as reinforcement. The objective, in these applications of the laminating art, has been to develop laminates with cloth-like attributes with respect to strength, noise, drape, handle, and absorbency.
Practitioners of the laminating arts have found it difficult or impossible to engender all of the above desired functional attributes in a single sheet. This is to say that, if in a conventional instance, the laminated sheets were combined and then impregnated by spraying or dipping with a migratory latex; the resulting laminated suffered in absorbency and in surface feel. Further, if such a through bonded laminate was given a centrally disposed layer of bonded scrim or continuous filament nonwoven reinforcement sufficiently strong to engender cloth-like strength, the resulting laminate was rendered stiff and unpliable. Similarly, if a laminate having a central impregnated layer is combined by heat and pressure after drying the central layer, the resulting laminate has been found relatively noisy.
In particular, practitioners of the laminating art, while showing improvement in their skills and materials selection, have found the diminishment or abrogation of noise, the rattle associated with paper sheets, to be a continuing probelm in nonwovens and laminates otherwise approaching the duplication of cloth-like physical properties.
In brief, although those skilled in the art of laminate preparation have continued to improve their products, their efforts, while producing laminates improved in many respects and used as substitutes for woven cloth in selected and restricted applications, have not yet resulted in laminates possessing the drape, strength and noise qualities of woven cloth.
Notable examples of processes for the preparation of sheet and laminate materials are set forth in early patents, for example, U.S. Pat. No. 1,660,924, issued to Ernest Hopkinson on Feb. 28, 1928, while later patents such as U.S. Pat. No. 2,668,787, issued to August F. Schramm, Jr. on Feb. 9, 1954, illustrate methods of reinforcement. Additional patents, for example U.S. Pat. No. 2,923,653, issued to Nathaniel A. Matlin and Benjamin B. Kine on Feb. 2, 1960; U.S. Pat. No. 2,931,749, issued to Benjamin B. Kine and Nathaniel A. Matlin on Apr. 5, 1960; U.S. Pat. No. 2,954,816 and U.S. Pat. No. 2,954,817, issued to Robert A. Havemann on Oct. 4, 1960; U.S. Pat. No. 3,063,454, issued to Herbert W. Coates and Roland A. Frate; U.S. Pat. No. 3,546,056, issued to Gordon D. Thomas on Apr. 29, 1968; U.S. Pat. No. 3,567,566, issued to Werner Bandel, Herbert Hilpert, Hans Treckmann and Ernst Pirot on Mar. 2, 1971 and U.S. Pat. No. 3,629,047, issued to Robert W. Davison on Dec. 21, 1971 have served to further the arts of sheet impregnation, laminati and reinforcement. Other patents, including Belgian Pat. No. 710,228, issued to Aktiebolaget Billingsfors-Langed on June 17, 1968; British Pat. No. 1,116,826, issued to Aktiebolaget Billingsfors-Langed on June 12, 1968; British Pat. No. 1,200,235, issued to Aktiebolaget Billingsfors-Langed on July 29, 1970 and British Pat. No. 1,185,227, issued to Consolidated Paper (Bahamas) Limited on Mar. 25, 1960 have similarly advanced the art of sheet lamination.
Further patents, which have disclosed improvements in the art of sheet lamination or materials used in laminates and wherein filament nonwovens are disclosed are U.S. Pat. No. 3,314,841, issued to Bruno Romanin on Apr. 18, 1967; U.S. Pat. No. 3,341,394 issued to George A. Kinney on Sept. 12, 1967; U.S. Pat. No. 3,600,262 issued to Daniel H. Frank on Aug. 17, 1971; U.S. Pat. No. 3,639,199 issued to Theodorus G. Brandts, Joseph A. Lichtenberger and Joseph M. Bentvelzen on Feb. 1, 1972; U.S. Pat. No. 3,674,594 issued to Leif R. Persson on July 4, 1972; U.S. Pat. No. 3,695,985 issued to Robert J. Brock and Gordon D. Thomas on Oct. 3, 1972; U.S. Pat. No. 3,770,562 issued to Nicholas S. Newman on Nov. 6, 1973 and U.S. Pat. No. 3,809,077 issued to Paul E. Hansen on May 7, 1974.
Applicants have unexpectedly discovered, however, that the cloth-like physical properties of tissue, nonwoven laminate constructions can be considerably enhanced and improved, with particular respect to noise or rattle diminishment, over the disclosures and suggestions available in the prior art.
The continuous filament nonwovens contemplated for use together with tissue layers in the present advantageous quiet, strong laminate are particularly processed and selected continuous filament nonwovens falling within the broad scope of U.S. Pat. No. 3,341,394, cited above. It is, however, considered critical to achievement of the present rattle diminishment, drape and handle objectives that the continuous filament nonwovens used be in a low specified weight range and have little or no inter-fiber bonding prior to impregnation, i.e., are only lightly bonded or substantially unbonded.
As will be more fully set forth below, the present improvement in laminate noise or rattle level to approach the noise level of cloth in comparison with laminates of like basis weight and strength is believed by applicants to stem from novel and unobvious selection juxtapositioning of laminate layer elements, particularly this juxtapositioning of a continuous filament only lightly bonded or unbonded nonwoven layer between at least two facing tissue layers of absorbent soft tissue paper, together with processing methods particularly combining the layers under low combining pressures while in the wet state prior to drying and curing of the resulting laminates. In particular, it is considered necessary to employ soft, tacky, nonmigratory latex binder solids in a viscous emulsion to achieve the present low noise, high strength laminates. It is further considered essential that the amount of binder solids applied to the continuous filament nonwoven laminate layer fall within a specified relatively high range for binder solids addition, although due to the low basis weight of the continuous filament layer, the resulting laminates have a relatively low amount of binder solids content, based on total laminate basis weight. Surprisingly the resilience and loft of the consolidated but only lightly bonded or substantially unbonded nonwoven continuous filament spunbonded web and the low combining pressures employed to bring together the present laminate layers in the wet state results in a relatively high thickness or loft laminate and also reduces noise or rattle in the resulting laminate without substantially affecting the strength and drape thereof. This result was unexpected by applicants, because increased thickness is normally associated with higher bending moments, together with decreased drapeability and handle.
An additional feature which can be incorporated in the present laminate is where, for example, different color, absorbency or surface texture characteristics are desirable in the two opposing laminate surfaces. Differences in these laminate attributes can be engendered in the present laminate, where they would be difficult or impossible to develop in woven materials, by facing layer selection and or mechanical and chemical treatments prior, during or subsequent to laminate formation.